As previously disclosed, because of the distortions and especially irreversible distortions when a sail has been overstressed, the restrictions on the wind speed are especially severe when the laminated sails are bieng used. Laminated sails distort precipitously beyond a yield point and the sail then loses its efficient lifting surface characteristics or is totally destroyed.
As consequence, modern backing fabrics have been employed to stabilize the laminate film, and the modern laminates consist predominantly of Mylar film with Dacron reinforcements and Mylar film with Kevlar reinforcements. Mylar is a film and Dacron is a fabric thread material of a polyester polymer. Mylar and Dacron are trademarks of the Dupont Company. Kevlar is an aramid polymer, and Kevlar is also a trademark of the Dupont Company. Thus the Dacron and Kevlar fabrics and reinforcements made from these materials have the essential function of stabilizing the laminated sail material as the forces are being imposed on the sail fabric or laminate with the fabric or laminate being the load bearing member of the sail.
In a similar manner, the Kevlar and Kevlar laminates (aramid polymers and the derivatives of the aramid family) are being increasingly used because the Kevlar material possesses extremely advantageous strength to weight ratios. Because of the very important weight reduction aloft, the sail construction described in my previous application has achieved substantial savings, e.g., up to about 50% for a mainsail for a 43 foot boat. This has the importance of reducing the pitching and yawing motion and the dynamic loading of a sail.
With less weight aloft, a boat pitches and yaws less, and therefore has a more efficient forward force. However, in the past, reduction of the weight for the sail was likely to increase the risk of distorting the sail.